pH project

[phpcmp]

I am doing research on mussels and I wanted to know how I could reduce the pH of seawater 8.29 so that I can test the effects of stress on the organism. I would like to get the pH to about 4 if that is possible and as high as 10 if that is possible.

 

[billsreef]

I'd suggest using controlled amounts of HCl (muriatic acid). The high side, simple bicarbonate should do the trick

 

[Travis L. Stevens]

Could you use Carbon Dioxide to lower the pH and Oxygen to raise it? You might not be able to swing it very far without killing the specimens with too much CO2. Also, I don't know what the limitations are in swinging with CO2/O2. Billsreef, any knowledge on this?

 

[fgarvine]

Vinegar on a drip will lower slowly and can easily be buffered. 4 wont be necessary with a mussel.

 

[fgarvine]

Vinegar on a drip will lower slowly and can easily be buffered. 4 wont be necessary with a mussel will it Bill??

 

[billsreef]

The CO2 would lower the pH, however, it will also effect the animals respiration negatively and add a seperate variable to the experiment. Hence my suggestion of HCl It will lower pH without effecting respiration.

 

[Spracklcat]

Bill, I was thinking the same thing--by changing the dissolved gases along with the pH you're not isolating a single variable and therefore are compromising the experiment. Whatever you add to alter pH should be something naturally in seawater; better yet duplicate the experiment using two different acids/bases to ensure that it is the pH change and not the additional chemical that is causing the effect.

Chris

 

[billsreef]

<a href=showthread.php?s=&postid=7148039#post7148039 target=_blank>Originally posted</a> by fgarvine
Vinegar on a drip will lower slowly and can easily be buffered. 4 wont be necessary with a mussel will it Bill??

Don't know why he wants to go as low as 4, I expect it's part of the experiment design. Be interesting to hear the results in any event

Vinegar (acetic acid) can also alter the carbon ratios in the water. I'm figuring he has good lab access to most any acid he needs, and the muriatic acid being nothing more than HCl will lower the pH and only alter the hydrogen and chloride ratios. It's the hydrogen part that will drop the pH, and the amount of chloride change will be quite negligable by comparisson to the total chloride in SW. It's the only acid I can think of that won't have any practical effect on anything other than the pH.

Chris,

:wavehand:

 

[Spracklcat]

Good point--and together with that, would dilute NaOH serve the same purpose, for raising the pH?

(Hi Bill, long time no see

 

[billsreef]

Christine,

Good idea with the NaOH

 

[John Karavias]

If Co2 is added to the system, Carbonic acid is formed. (H2Co3). That will lower the pH and NaoH will raise it. However lowering the pH with Co2 will alter respiration of organisms. Maybe Calipera, can't spell it, will help with that.

 

[boxfishpooalot]

Caulerpa will raise the ph, not lower it. But you would need an extravagent amount to do it. Eventually it would die at such a low ph, causeing a spoiled tank experiment.

 

[John Karavias]

Thanks boxfish,

I had no idea caulerpa does the opposite